/Engine/Source/Runtime/RenderCore/Public/GBufferInfo.h
If we pass in 4 values, it means we also need to pack the bits
FGBufferPacking ( int32 InTargetIndex, int32 InSrcChannelIndex, int32 InDstChannelIndex, int32 InSrcBitStart, int32 InDstBitStart, int32 InBitNum )